package demo;
import java.util.Scanner;
public class Test2 {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        int cost[] = new int [n];
        int dp[] = new int [n+1];
        for(int i = 0; i<n; i++){
            cost[i] = in.nextInt();
        }
        for(int i = 2; i<= n;i++){
            dp[i] = Math.min(dp[i-1]+cost[i-1],dp[i-2]+cost[i-2]);
        }
        System.out.println(dp[n]);
    }
}